[Samba] slow samba write performance

[Depeche]

Hi,
I have a problem, problem is slow samba write performance.I tested samba copy and ftp copy, result and machine spec;

Samba PC
P4 3 ghz / 2 gb Ram
1 x 80 gb HDD(for system)
4 x 250gb sata hdd (software raid /dev/md0)^
3com gigabit ethernet

Windows Pc
AMD 2500+ / 5123mn ram
1 x 80 gb hdd (c:\)
1 x 160 gb hdd (d:\)
gigabit ethernet

test results;

windows hdd to hdd copy
Source    File Size            Target             Time            
c:\            713+715MB      d:\                110sn        12.989 kb/sec
d:\            713+715MB      c:\                 59sn         24218  kb/sec

Samba Copy

c:\            713+715MB      /dev/md0        183sn        7808 kb/sec
d:\            713+715MB      /dev/md0        183sn        7808 kb/sec ---->samba write slow than ftp write
/dev/md0   713+715MB      c:\                  60sn        23814 kb/sec
/dev/md0   713+715MB      d:\                  86sn        16614 kb/sec
c:\            713+715MB      /home            144sn        9285 kb/sec       

 FTP copy 
c:\            713+715MB      /dev/md0         92sn        15531 kb/sec
d:\            713+715MB      /dev/md0         80sn        17861 kb/sec----->ftp copy > samba copy %128 
/dev/md0   713+715MB      c:\                  75sn        19051 kb/sec
/dev/md0   713+715MB      d:\                  86sn        15876 kb/sec

hdparm /dev/md0 results;

Timing cached reads 3980mb in 2.00 sec=1989.88 mb/sec
Timed buffered disk reads: 232mb in 3.00 sec=77.33 mb/sec

samba settings
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192 
IPTOS_LOWDELAY 

Why slow samba than ftp?

Thanks